Two experimentation setups are available: the indoor lab and the outdoor lab.

In order to conduct experiments in the LTE+ testbed, participants are required to bring their spectrum sensing and/or secondary system hardware to Dresden, if the experiment cannot be performed by a USRP or HaLo device. In order to pre-evaluate certain theories and algorithms, a testbed reference signal in the form of baseband I/Q samples can be provided. Further, during the experiments it is possible to dump transmitted and received signals in the same format. This allows for offline post-processing of the signals, evaluation of the signals and replay in other testbeds.

It is important to distinguish if a downlink (DL) or an uplink (UL) experiment is desired.

In uplink experiments, it is possible to serve up to 4 UEs. The UEs use 1 antenna for transmission, while the eNBs can receive with 1 or 2 antennas. The resolution for scheduling a transmission is 1 ms, which corresponds to 1 TTI (transmission time interval). Scheduling can be done for a total duration of several minutes. The number of occupied PRBs is either 10, 20, 30 or 40 (cf. Table 1). QPSK, 16QAM and 64QAM modulation are supported.

In downlink, up to 4 UEs and up to 4 eNBs can be used simultaneously. The eNBs can transmit with up to 2 antennas and the UEs can receive with up to 2 antennas, thus up to 2 streams per UE can be sent. Time resolution is 1 ms corresponding to 1 TTI (same as UL). The number of occupied PRBs can be 12, 24, 36 or 48 (cf. Table 2).

The evaluation of an experiment happens via dumps of the received signals at the UEs / eNBs. While in the UL, signal dumps can be recorded for all eNBs in synch, the dumping process needs to be initiated manually and out of synch in the DL.

The signal dumps contain the received time samples as well as additional control information. Further processing in Matlab allows derivation of indicators like SINR, BLE, etc. in semi-realtime/offline.

The performance evaluation of experiments can be performed in real-time as well as semi real-time and offline. Real-time measures include

• Received Signal Strength Indicator (RSSI),
• Reference Signal Receive Power (RSRP),
• Path loss, and
• Channel Quality Indicator (CQI; derived from SINR).

In semi real-time, additionally QAM constellations and block error rate (BLER) can be monitored via file dump of I/Q samples and Matlab post processing. Further performance measures could be obtained in offline processing from those file dumps.

Please click on the thumbnail below to get an overview picture of the usage overview in LTE advanced testbed.